Recent experiments have demonstrated that infant lid-suture in tree shrews (Tupaia glis) results in the development of severe myopia (-20 D average). Since the effect occurs monocularly, producing adults with one emmetropic and one myopic eye, this lid-suture model has allowed us to make detailed comparison of the experimental myopic eye with a genetically identical normal control. During the past grant period we were able to demonstrate that in addition to being axially elongated, the myopic eyes exhibited zonular dysplasia and reduced lens development. Taken together, these data support the hypothesis that accommodative activity influences growth of both lens and globe and that this relationship is crucial to the development of emmetropia as well as myopia. During the proposed grant period we plan to test further this hypothesis by manipulating accommodation through visual experience and other means and by examining in more detail the anatomic anomalies associated with the lid-suture myopia.